Translucent Wall Element and Motor Vehicle Comprising Such an Element

ABSTRACT

A translucent wall element comprising a first plate-like member ( 1 ) of a transparent material and a second plate-like member ( 2 ) of a translucent material positioned at the outer side of said first plate-like member ( 1 ) substantially parallel to said first plate-like member. Means for coupling light into said first plate-like member are present. The surface ( 7 ) of said first plate-like member ( 1 ) is provided with spots of light-distribution means ( 8 ) at the side facing the second plate-like member ( 2 ). The light-distribution means ( 8 ) direct light radiation towards the other side of said first plate-like member ( 1 ).

The invention relates to a translucent wall element comprising a first plate-like member of a transparent material and a second plate-like member of a translucent material positioned at an outer/first side of said first plate-like member substantially parallel to said first plate-like member. Such a translucent wall element may be a part of a wall of an enclosed room in which persons may be present, or a part of a roof of a passenger compartment of a motor vehicle. An inner/second side of the translucent wall element is the side facing the inside of the passenger compartment or room, and the second side of the translucent wall element is the other side, for example, facing the open air outside.

A translucent wall element comprising two or more translucent plate-like members, together forming a sandwich structure, is a customary translucent wall element for the passenger compartment of a motor vehicle. Such a sandwich structure may comprise three layers, an outer layer and an inner layer, both being plate-like members of glass, and a layer of plastic material, for example, polyvinyl butyral (PVB) may be present between these plate-like members of glass. The glass plate-like members have a normal thickness of 2.1 mm, and the PVB layer has a normal thickness of 0.5 mm, so that the wall element has a total thickness of, for example, 4.7 mm.

To improve the atmosphere in the passenger compartment of a motor vehicle, the roof of the passenger compartment can be provided with such a translucent wall element, so that light radiation can enter the passenger compartment from above. The transmission of light can be reduced by means of a coating at the outer side of the second plate-like member (the outer glass plate), or by making use of low-transmission glass. Such a reduction of light transmission may be desired to prevent direct radiation of sunlight entering the passenger compartment of the motor vehicle.

However, at night, when it is dark outside, the translucent wall element in the roof of the passenger compartment of the motor vehicle does not improve the atmosphere in the passenger compartment, and may even form an inconvenient “black hole”. It has been found that the atmosphere in the passenger compartment of a motor vehicle can be improved by generating light radiance from the roof of the passenger compartment.

Document US-A-2002/0167820 describes a light-guiding system for improving the lighting conditions in the passenger compartment of a motor vehicle, in which a plate-like light guiding element is arranged in the area of the interior lining of the vehicle roof Light is coupled into the light-guiding element through one or more lateral surfaces at the edge of the light-guiding element, and light is emitted through the large inner surface (front surface) of the light-guiding element into the passenger compartment of the motor vehicle in a homogeneous manner.

It is an object of the invention to provide a translucent wall element, in particular a translucent wall element which is to be mounted in the roof of the passenger compartment of a motor vehicle and can transmit light radiation from outside, but also emit light radiance which is mainly emitted, and preferably substantially completely emitted, from the inner side of the translucent wall element into the passenger compartment of the motor vehicle, or into the room in which persons may be present, as the case may be.

To achieve this object, means for coupling light into said first plate-like member are present, in particular at one or more lateral surfaces of said first plate-like member, while the surface of said first plate-like member is provided with spots of light-distribution means at the side facing the second plate-like member (first side), which light-distribution means direct light radiation towards the other side (the inner side) across said first plate-like member so as to couple out light radiation through the surface at the inner side of the first plate-like member of the translucent wall element. By locating the light-distribution means at the first side of the light-guiding first plate-like member, light radiation will mainly be coupled out through the second side of said first plate-like member, in order to be radiated into the interior of the room or into the passenger compartment of the motor vehicle.

Appropriate materials for the light-guiding first plate-like member are transparent thermoplastics, in particular polyvinyl butyral (PVB), or polymethyl methacrylate (PMMA), or polycarbonate (PC). Also glass can be used as a light-guiding material, in which, preferably, Fe₂O₃ is removed from the glass material.

In one preferred embodiment, the material of said second plate-like member is glass which is preferably provided with means for reducing light transmission through it, for example, a coating at its outer surface or light-absorbing material in the glass. Such a second plate-like member protects the first side of the first plate-like member against scratches and other damage, and the light-transmission reducing means decrease the transmission of daylight, and, in particular, the transmission of direct radiation of sunlight.

In a further preferred embodiment, said light-distribution means are spots of reflecting material on the outer surface of the first plate-like member. Such spots of reflecting material may be dots of white paint, or dots of a material comprising a metal, etc. These spots can be applied easily on the outer surface of the first plate-like member.

In another preferred embodiment, said light-distribution means are rugged spots on the first side of the first plate-like member. In this case, no material is applied on the outer surface, but the outer surface is locally treated by means of a material-removing operation or, preferably, by means of a melting operation, wherein a small portion of the material at the outer surface of the first plate-like member is melted by means of, for example, a laser beam.

In another preferred embodiment, said light-distribution means are recesses, each having an inner surface which is inclined with respect to the plane of the first plate-like member. Such inclined surfaces reflect the light radiation in the light-guiding first plate-like member in such directions that at least a portion of the reflected light radiation will be coupled out through the second side of said first plate-like member, so that it is radiated into the interior of the room or into the passenger compartment of the motor vehicle.

The recesses may have any shape mainly having surfaces which are inclined with respect to the second side of the first plate-like member, but preferably the shape of cones or pyramids. If the material of the first plate-like member is a thermoplastic shaped by means of, for example, an injection molding process, such recesses in the outer surface can be easily made in this process.

In one preferred embodiment, the light-distribution means at the surface of the first plate-like member are covered with spots of a material which is opaque to visible light so as to further reduce light radiation from the first plate-like member to the first side of the translucent wall element. These spots are preferably slightly larger than the light-distribution means, so that they cover the whole light-distribution means and its edge area.

The material of said spots is preferably reflective at its surface abutting the first plate-like member, so that light radiation is reflected back into the first plate-like member and can be coupled out at the other side of this member, and increases the radiation into the interior of the room or into the passenger compartment of the motor vehicle, as the case may be. Said material of said spot is preferably a metal, more preferably, aluminum.

In a further preferred embodiment, a cladding, i.e. a layer of a cladding material, is present between said first plate-like member and said second plate-like member. The cladding preferably has a thickness of at least about 1.5 μm, i.e. about twice the wavelength of light. Such a cladding material has a relatively low index of refraction, which is substantially lower than the index of refraction of the material of the first plate-like member, so that an effective reflection of light radiation, which is guided in the first plate-like member, is ensured, and such a reflection will not be affected by optical contact of the surface of the first plate-like member with other objects.

In one preferred embodiment, a third translucent plate-like member, preferably made of glass, is present at the second side of said first plate-like member substantially parallel to said first plate-like member, while a layer of a cladding material is preferably present between said first plate-like member and said third plate-like member. In this preferred embodiment, the translucent wall element preferably comprises two plates of glass (the second and the third plate-like members) with a light-guiding member (first plate-like member) in between and the light-distribution means at its outer surface, wherein a layer of a cladding material is present at each side of the light-guiding member.

The invention also relates to a motor vehicle having a passenger compartment, wherein the roof of the passenger compartment is provided with a translucent wall element comprising a first plate-like member of a transparent material and a second plate-like member of a translucent material positioned at the first side of said first plate-like member substantially parallel to said first plate-like member, wherein means for coupling light into said first plate-like member are present, and wherein the surface of said first plate-like member is provided with spots of light-distribution means at the side facing the second plate-like member, which light-distribution means direct light radiation towards the second side of said first plate-like member.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawing,

FIG. 1 is a sectional view of a part of a first embodiment of a translucent wall element;

FIG. 2 is an enlarged representation of a portion of FIG. 1; and

FIG. 3 is a sectional view of a part of a second embodiment of a translucent wall element.

FIGS. 1 and 2 represent diagrammatically a small portion of the first embodiment of a translucent wall element comprising a first plate-like member 1 made of a transparent material having a relatively high index of refraction, i.e. higher than air and higher than the surrounding materials that make optical contact with the first plate-like member 1, so that light radiation can be coupled into, and guided in, the transparent material of the first plate-like member 1. The light radiation can be coupled in through the lateral surfaces at the edges of the first plate-like member 1 (not shown in the Figures), and reflects against both the first side 20 and the second side 21 of the first plate-like member 1, so that it will be kept and guided in the transparent material of the first plate-like member 1, as is well known in the prior art. The transparent material of the first plate-like member 1 is, for example, polyvinyl butyral (PVB). This material has an index of refraction of about 1.485, which is substantially equal to the index of refraction of glass, which is about 1.50.

Plate-like members 2, 3 of glass are present at the first respectively the second side of, and parallel to, the first plate-like member 1. Second plate-like member 2 is present at the first side 20 (the upper side in the Figures) of the first plate-like member 1, and third plate-like member 3 is present at the second side 21 (the lower side) of the first plate-like member 1. The first plate-like member 1 and the second and third plate-like members 2, 3 enclose claddings 4, 5, i.e. layers of a cladding material having a relatively low index of refraction, which is substantially lower than the index of refraction of the material of the first plate-like member 1, so that an effective reflection of light radiation, which is guided in the first plate-like member 1, is ensured, and such a reflection will not be affected by optical contact of the surface of the first plate-like member with other objects. The claddings 4, 5 have to make optical contact with the first plate-like member 1. Such a cladding material is, for example, transparent silicone rubber, which also functions as an adhesive, keeping the plate-like members 1, 2, 3 together, so that a firm sandwich structure of the translucent wall element is obtained. Light radiation, for example, light ray 6, which is guided by the first plate-like member 1, will be reflected at the surface 7 of the plate-like member 1, provided that its angle of incidence is larger than a given value, which value depends on the indexes of refraction of the materials of the first plate-like member 1 and the material of the claddings 4, 5. As is shown in FIG. 1, the angle of incidence of the light ray 6 is equal to the angle of reflection of this light ray 6.

As represented in FIG. 1 and shown on a larger scale in FIG. 2, light distribution means, i.e. spots 8 for example, dots of white paint, are applied on the surface 7 at the first side 20 of the first plate-like member 1 (the upper side in FIG. 1). The white paint of the dots 8 makes optical contact with the material of the first plate-like member 1, so that a light ray 9 that reaches such a dot 8 of white paint will not be reflected at an angle equal to the angle of incidence, but will be scattered into all directions. Light radiation will then be coupled out, mainly at the inner side 21 (the lower side in the Figures) of the first plate-like member 1. Such light radiation will pass through the third plate-like member 3 and leave the translucent wall element at its inner side (the lower side in the Figures).

Since the dots 8 comprise only a thin layer of white paint, some light radiation scattered from it may also be directed upwards (in the Figure). To prevent light radiation from leaving the translucent wall element at the outer side (the upper side in the Figures), spots of a thin layer 10 of aluminum cover the dots 8 at the upper side. The layer 10 of aluminum is opaque to light radiation and reflects the light radiation downwards, so that it increases the efficiency of the light radiation from the inner side (lower side) of the translucent wall element.

If the translucent wall element is used in the roof of a vehicle, the second plate-like member 2 may be grayish and light-absorbing so as to keep too much sunlight out of the passenger compartment of the vehicle during daytime. When it is dark outside, light can be coupled into the first plate-like member 1, so that some light radiation enters the passenger compartment from above, which is convenient to the passengers in the vehicle.

FIG. 3 represents a portion of the translucent wall element in said second embodiment. First plate-like member 11 made of, for example, polycarbonate (PC), is positioned between second plate-like member 12 and third plate-like member 13, both made of glass. Layers 14, 15 of a cladding material are present between the first plate-like member 11 and the second and third plate-like members 12, 13. The surface of the outer side of first plate-like member 11 is provided with recesses 16, each recess 16 having a pyramidal shape, with all surfaces of the recess being inclined with respect to the plane of the first plate-like member 11. The recesses 16 may be filled with air or another gas, as is shown in FIG. 3, but they may also be filled with the cladding material of layer 14.

Similarly as in the first embodiment, light radiation can be coupled into said first plate-like member 11, and when such light radiation is reflected by the inclined surface of one of the recesses 16, at least a part of it will be directed downwards (in FIG. 3), so that it leaves the first plate-like member 11 and the translucent wall element after it has passed through the transparent cladding 15 and the transparent third plate-like member 13.

In the second embodiment of the translucent wall element, the outer side of the second plate-like member 12 is provided with a coating 17 of a light-absorbing material so as to reduce the light transmission through the translucent wall element.

The two embodiments of the translucent wall element as described above are only examples; a great many other embodiments and variations are possible. 

1. A translucent wall element comprising a first plate-like member (1) of a transparent material and being arranged substantially parallel to a second plate-like member (2) of a translucent material, which second plate-like member faces the first plate-like member at a first side (20) of said first plate-like member, characterized by means for coupling light into said first plate-like member, a surface of the first side of said first plate-like member being provided with spots of light-distribution means (8), which light-distribution means direct light radiation towards a second side (21) opposite the first side of said first plate-like member and across said first plate-like member.
 2. A translucent wall element as claimed in claim 1, characterized in that said second plate-like member is made of glass which is provided with light-transmission reducing means.
 3. A translucent wall element as claimed in claim 1, characterized in that said light-distribution means comprise spots of reflecting material on the surface of the first plate-like member.
 4. A translucent wall element as claimed in claim 1, characterized in that said light-distribution means comprise rugged spots on the surface of the first plate-like member.
 5. A translucent wall element as claimed in claim 1, characterized in that said light-distribution means comprise recesses, each having an inner surface which is inclined with respect to the surface (7) of the first plate-like member.
 6. A translucent wall element as claimed in claim 1, characterized in that the light-distribution means at the surface of the first plate-like member are covered with second spots of a material which is opaque to visible light.
 7. A translucent wall element as claimed in claim 6, characterized in that the material of said second spots is reflective at its surface abutting the first side of the first plate-like member, said material of said spot being preferably a metal, more preferably aluminum.
 8. A translucent wall element as claimed in claim 1, characterized in that a layer of a cladding material, having a lower index of refraction than the index of refraction of the material of the first and the second plate-like member, is present between said first plate-like member and said second plate-like member.
 9. A translucent wall element as claimed in claim 1, characterized in that a third translucent plate-like member is provided at the second side of said first plate-like member and is arranged substantially parallel to said first plate-like member.
 10. A car roof canopy characterized in that it comprises a translucent wall element as claimed in claim
 1. 11. A motor vehicle having a passenger compartment, characterized in that the roof of the passenger compartment is provided with a translucent wall element as claimed in claim
 1. 